body{font-family:Arial;background:#f2f2f2;padding:20px}
.container{max-width:400px;margin:auto;text-align:center}
.sensor-box{background:#fff;margin:10px;padding:10px;border-radius:6px}
.btn-group{display:flex;justify-content:space-around}
.btn{padding:10px;color:#fff;border:0;border-radius:6px}
.start{background:#28a745}.stop{background:#dc3545}.reset{background:#007bff}